Technical field
[0001] The present invention belongs to the sector of brush cutters for mowing lawn and
vegetation, i.e. to those devices wherein a rotary head drives into rotation a flexible
wire, which operates as a cutting element.
[0002] Specifically, the present invention refers to a head which internally accommodates
a sprocket on which a cutting wire is wound, whose end sections project from the head
and cut the vegetation whenever the head rotates.
Present status of the art
[0003] Brush cutter apparatuses are known for a long time which comprise a rotary head located
at an end of a transmission rod, where a handle is applied by means of which an operator
operates the apparatus, which transmits the rotatory motion of the motor to the cutting
tool.
[0004] Usually the brush cutter apparatus is driven by a motor, typically an electric or
internal combustion one, and the rotary head comprises a support element which is
driven into rotation by the driving shaft of the brush cutter; in turn, the head drives
one or several cutting elements into rotation.
[0005] Initially said cutting elements were made up of metal blades, however the latter
were very dangerous for users, in that they might cause even major injuries.
[0006] This is the reason why rotary heads have been developed, which remove vegetation
without using blades, thanks to the cutting action exerted by a flexible wire, made
from a polymeric material, whose end comes out from the rotary head and, under the
action of the centrifugal force, defines a cutting plane.
[0007] The flexible cutting wire is usually wound around a sprocket which is located internally
to the rotary head.
[0008] Unavoidably, in operation, the end of the wire wears out or breaks and consequently
it shall be replaced, by extracting a new section of wire out of the sprocket. A number
of systems have been developed for this purpose, aiming at not being obliged to switch
the brush cutter off in order to manually extract the wire.
[0009] Some rotary heads are provided with a mechanism which allows to press the base element
of the head to ground for a while to unwind a predetermined length of the cutting
wire, in order to recover the ends of the wire that had worn out. The rotary heads
of this type comprise a sprocket preset to wind a coil of flexible wire.
[0010] A typical functional diagram comprises a head internally to which a sprocket is associated
with, movable between a work position, wherein it is rotationally integral with the
head, and a wire extraction position, wherein the sprocket does not rotationally engage
the rotary head; in the latter position, the action exerted by the centrifugal force
causes the extraction of a predetermined section of the cutting wire.
[0011] In particular, heads have been developed wherein the sprocket has a special toothing
below which co-operates with another special toothing formed in the housing underneath,
so that whenever the sprocket moves upwards it disengages itself from the driving
action exerted by the rotary head. After feeding the cutting wire, the sprocket, pushed
by elastic means, goes back to its lower position and rotationally engages the rotary
head again.
[0012] Usually the box-like body that accommodates the sprocket consists of two half-shells,
coupled with each other by way of elastic snap connection means. These are coupling
means that comprise male connectors, consisting of elastic tangs with a wedge-shaped
end featuring a projecting base, so that, after penetrating their respective insertion
seats, they cannot be taken off by a simple traction, but it is necessary to press
the end portion of the male connector inwards. In this way the two half-bodies, after
being coupled together, are in a precisely defined mutual position.
[0013] In operation, the centrifugal force pushes the tangs outwards and further consolidates
coupling.
[0014] Whenever the sprocket gets empty, it is necessary to rewind it with a new cutting
wire; for this purpose, a number of solutions have been developed; in the first models,
in order to re-load the wire onto the sprocket it was necessary to open the head,
to take the sprocket out therefrom and to manually re-wind the wire, and the reinsert
the sprocket into the head and to close it again.
[0015] This operation is difficult to perform for many users.
[0016] This is the reason why heads for brush cutters have been developed wherein it is
possible to re-wind the wire without being obliged to open them; in this type of heads,
the operator shall manually rotate a part of the head, while simultaneously pressing
it in order to disengage the sprocket and make it possible for it to rotate with respect
to the rest of the head.
[0017] The most popular known solutions comprise a base knob integral with the sprocket
which comes out below from the shell; it is possible to make the sprocket rotate by
pressing the knob toward the inside of the shell; this axial movement makes it possible
to have a new section of the cutting wire automatically retracted and to re-load the
sprocket by re-winding the wire.
[0018] The known solutions have a number of drawbacks, in particular it is necessary that
the base knob have a remarkable thickness, in order for it to be grasped by the operator
who, in order to re-load the wire, shall push the knob towards the inside of the shell
and, simultaneously, make it rotate around its axis to wind the newly fed cutting
wire.
[0019] The remarkable dimensions of the base knob in the axial direction are such that the
cutting wire is not capable of cutting the vegetation close to the ground; in addition,
the operator shall make attention to leave a space between his/her hand and the shell
when grasping the knob, to make it possible for the knob to partially come back to
within the shell.
[0020] In addition, it shall be possible for the heads of the brush cutters to be easily
opened in order to clean them while they are being operated and it shall also be possible
to completely disassemble them in order to perform maintenance operations thereon;
many types of heads do not allow to perform these operations easily, because they
are difficult to open without using tools and/or because they are constructed in such
a way that, when opened, they decompose in a high number of small-size component parts,
which implies a high risk of getting lost when operating in the country.
Objects and summary of the invention
[0021] A first object of the invention is to provide a head for brush cutters wherein the
cutting wire can be fed easily, by striking it to ground, and simultaneously to provide
a lawn mower head simple to assemble and disassemble, as well as easy to re-wound
with a cutting wire even by operators who wear work gloves.
[0022] A non-secondary object of the present invention is to provide a head for brush cutters
that allows to mow the vegetation close to the ground.
[0023] Further objects and advantages of the invention will be apparent to those skilled
in the art upon reading the following text.
[0024] The heads of this type are rotationally connected to the shaft of the brush cutter
according to known means.
[0025] The above described objects are achieved by a new-concept head wherein a projecting
base knob is replaced by an innovative base cap.
[0026] More specifically, the present invention consists of a head comprising a rotary shell
slidingly coupled with a feeding assembly, co-operating with each other in an innovative
manner.
[0027] The rotary shell comprises an upper cover, rotationally connected to the shaft of
the brush cutter and connected to an annular body underneath, to form a box-like body
internally to which there is slidingly accommodated the sprocket that carries the
cutting wire, the latter going out from the shell through appropriate side openings.
[0028] In a preferred embodiment, the connection between the cover and the annular body
is a reversible one, in order to make it easier to disassemble the head.
[0029] The upper face of the annular body includes rotatory motion transmission means which
engage corresponding rotatory motion reception means that are present in the lower
portion of said sprocket; contrast means of an elastic type are interposed between
the top of the latter and the lower part of the upper cover, whereby the sprocket
is pushed against the annular body underneath which transmits the rotatory motion
thereto.
[0030] The sprocket is in turn connected to an innovative base cap, external to the rotary
shell and located below the annular body, with which it forms the feeding assembly,
and consequently the latter is slidingly associated with the rotary shell.
[0031] According to a particularly comfortable and functional version, the sprocket is connected
to the base cap reversibly, so as to make it easier to disassemble the head.
[0032] In order to re-load the sprocket, the operator shall press the base cap and simultaneously
rotate it; in the case of the head according to the present patent application, the
shape of the cap makes it easy for an operator to grasp it while wearing a glove and
to press it against the inside of the shell and to simultaneously make it rotate in
order to re-wind the newly fed wire, whereby it is much simpler to re-load the wire
than in the case of heads having a projecting base knob.
[0033] In operation, in order to lengthen the wire that has worn out it is sufficient for
the operator to strike the base cap to ground, so as to make the sprocket slide upwards
and make it disengage from the annular body that transmit motion thereto.
[0034] The centrifugal force makes the wire come out and the elastic contrast means push
the sprocket against the annular body again, so as to engage the means that transmit
motion between the latter and the sprocket again.
Brief description of the drawings
[0035]
Figure 1 shows an exploded top view of an embodiment of the head according to the present
patent application. The figure shows: rotatory motion transmission means (13) which
engage corresponding reception means (33) of a sprocket (3), longitudinal ridges (25),
the lateral surface (24) of a base cap (2), connection means (21) whose ends include
a corresponding wedge-shaped ridge (22) which engages a corresponding insertion seat
(32) after crossing a corresponding longitudinal slit (31), longitudinal slots (23)
which are engaged by longitudinal ridges (34), transversal slits (16) of internal
removable bushings (15), and reversible connection means (11) whose ends include a
respective wedge-shaped ridge (12) which engages a corresponding insertion seat (42)
present in said cover (4). The figure also shows elastic contrast means (5), a washer
(6), and side containment means (14) on the upper face of an annular body (1).
Figure 2 shows a bottom exploded view of the head according to the previous figure, which
highlights the side openings and transversal ridges (41) on the cover (4), besides
the inner lateral surface (17) of the annular body (1).
Figure 3 shows a half-section of the head in a retracted cutting wire feeding position.
Figure 4 shows a half-section of the head in a retracted cutting wire feeding position.
Detailed description of an embodiment of the invention
[0036] In a preferred embodiment, the head for brush cutters according to the present patent
application comprises a sprocket (3) on which a cutting wire is wound, the sprocket
being accommodated inside a rotary shell which receives motion from the motor of the
brush cutter and is formed of an upper cover (4) connected to a lower annular body
(1).
[0037] The connection between the cover (4) and the annular body (1) is a reversible one
and, in the embodiment shown in the figures, it is implemented by way of male connectors
having the form of elastic snap tangs which longitudinally rise up from the upper
face of said annular body (1) and whose ends include a respective wedge-shaped ridge
(12) which engages a corresponding insertion seat (42) present in said cover (4) .
[0038] The sprocket (3) is rotationally and slidingly associated with the annular body (1)
underneath, whose upper face is provided with side containment means (14) which define
an at least partially cylindrical cavity, which receives the sprocket (3) and features
side openings to make it possible for the wire to go out.
[0039] In the embodiment here described the sprocket (3) is reversibly connected to a base
cap (2) by way of connection means (21) which originate from the upper face of the
base cap (2) and whose ends engage corresponding insertion seats (32), after crossing
longitudinal slits (31) present in the body itself of the sprocket (3).
[0040] In a particularly practical and functional embodiment said connection means are reversible
so as to allow for an easy and quick disassembling of the head; they can be formed
of snap tangs whose ends feature a wedge-shaped ridge (22).
[0041] The annular body (1) receives motion from the cover (4) and transmits it to said
sprocket (3) thanks to rotatory motion transmission means (13) present on its upper
face which engage corresponding rotatory motion reception means (33) present in the
lower part of said sprocket (3) whenever the latter is kept pressed down against said
annular body (1) by elastic contrast means (5).
[0042] Preferably are said rotatory motion transmission means (13) of a unidirectional type
and in a practical embodiment the elastic contrast means (5) comprise at least one
helical spring.
[0043] Whenever the operator strikes the base cap (2) to ground, the action of the elastic
contrast means (5) is overcome and the sprocket (3) moves from the extended work position
to the retracted wire feeding position, in this way the rotatory motion transmission
between the annular body (1) and the sprocket (3) is interrupted, i.e. the rotatory
motion reception means (33) disengage themselves from the rotatory motion transmission
means (13).
[0044] During the mutual rotation of the sprocket with respect to the annular body the centering
of the two elements is provided by the contact between the inner lateral surface (17)
of the annular body (1) and the outer lateral surface of the cylinder defined by some
longitudinal ridges (34 and 25) projecting from the lower face of the sprocket (3)
and from the inner face of said base cap (2) respectively.
[0045] According to a preferred embodiment of the invention, a washer (6) is interposed
between the lower portion of said elastic contrast means (5) and the sprocket (3)
underneath, whose outer lateral surface is in contact with the inner lateral surface
of said elastic tangs, so as to prevent the latter from disconnecting from the sprocket
(3).
[0046] Conveniently the side openings comprise respective removable internal bushings (15)
which guide the extraction of the cutting wire which crosses them; in order to reduce
wear and tear and to increase the effects of the centrifugal force, these bushings
are often made from metal. According to an effective embodiment, said removable internal
bushings (15) are open above and define a transversal slit (16).
[0047] Advantageously transversal ridges (41) project below from said cover (4) and engage
respective transversal slits (16) of said removable internal bushings (15) so as to
further stabilize the cutting wire and reduce the stresses induced by transmission
of motion onto the elastic tangs.
[0048] A more stable coupling is obtained between the elements of the feeding assembly thanks
to the sliding engagement of some ridges (34) which project from the lower part of
the sprocket (3) to as many longitudinal slots (23) cut in the internal part of said
base cap (2).
1. A head for brush cutters comprising a sprocket (3) for a cutting wire, rotationally
and slidingly associated with an annular body (1) underneath, the latter provided
above with side containment means (14) which define an at least partially cylindrical
cavity, which receives said sprocket (3), also including side openings to make it
possible for the wire to go out; said sprocket (3) being connected to a base cap (2)
underneath by way of connection means (21) which slidingly cross said annular body
(1), within which they are free to rotate; said annular body (1) being in turn connected
to a cover (4) placed above which receives motion from the brush cutter and transmits
it to said annular body (1), thus co-operating below with said sprocket (3) by way
of elastic contrast means (5), the upper face of said annular body (1) comprising
rotatory motion transmission means (13) which engage corresponding rotatory motion
reception means (33) present in the lower part of said sprocket (3), whereby pushing
said base cap (2) upwards results in overcoming the action exerted by said elastic
contrast means (5) and said sprocket (3) moves from an extended work position to a
retracted wire feeding position, thus interrupting the rotatory motion transmission
between said annular body (1) and said sprocket (3), characterized in that said base cap (2) radially extends beyond the central hole of said annular body (1).
2. The head for brush cutters according to the previous claim 1, characterized in that said base cap (2) radially extends beyond the outer lateral surface of said annular
body (1).
3. The head for brush cutters according to the previous claim 2, characterized in that the lateral surface (24) of said base cap (2) longitudinally extends upwards and
at least partially winds said annular body (1).
4. The head for brush cutters according to any of the previous claims, characterized in that said rotatory motion transmission means (13) are of a unidirectional type.
5. The head for brush cutters according to any of the previous claims, characterized in that said connection means (21) are reversible.
6. The head for brush cutters according to any of the previous claims, characterized in that said connection means (21) comprise male connectors in the form of elastic snap tangs
which longitudinally rise up from the upper face of said base cap (2) and whose ends
include a respective wedge-shaped ridge (22) which engages a corresponding insertion
seat (32) present in the upper part of said sprocket (3), after crossing corresponding
longitudinal slits (31) present in the body of said sprocket (3).
7. The head for brush cutters according to any of the previous claims, characterized in that said annular body (1) is connected to said cover (4) by way of reversible connection
means (11).
8. The head for brush cutters according to the previous claim, characterized in that said reversible connection means (11) comprise male connectors in the form of elastic
snap tangs which longitudinally rise up from the upper face of said annular body (1)
and whose ends include a respective wedge-shaped ridge (12) which engages a corresponding
insertion seat (42) present in said cover (4) .
9. The head for brush cutters according to any of the previous claims, characterized in that a bushing (6) is interposed between the lower portion of said elastic contrast means
(5) and the sprocket (3) underneath, the outer lateral surface of the bushing is in
contact with the inner lateral surface of said connection means (21) so as to prevent
the latter from disengaging said sprocket (3).
10. The head for brush cutters according to any of the previous claims, characterized in that said side openings of said annular body (1) comprise respective removable internal
bushings (15) through which the cutting wire goes out.
11. The head for brush cutters according to the previous claim 11, characterized in that each of said removable internal bushings (15) is open above and defines a transversal
slit (16).
12. The head for brush cutters according to the previous claim 10, characterized in that transversal ridges (41) project from the lower face of said cover (4) and engage
said transversal slits (16) of said bushings (15) respectively.
13. The head for brush cutters according to any of the previous claims, characterized in that the inner part of said base cap (2) comprises longitudinal slots (23) which are slidingly
engaged by as many longitudinal ridges (34) which project from the lower part of said
sprocket (3).
14. The head for brush cutters according to any of the previous claims, characterized in that said elastic contrast means (5) comprise at least one helical spring.